Closure system

ABSTRACT

A closure system for an entranceway having a door mounted to open and close the entranceway. A perforated sill, in combination with a source of radiant energy provides a plurality of vertical beams of radiant energy spaced across the entranceway. A detector device is mounted to be responsive to at least one of the beams to detect interruption of radiant energy to the detector device by an object in the entranceway. In a preferred embodiment, the source of radiant energy includes energy having a wavelength in the visible spectrum, highlighting the sill as well as forming an operative portion of the object detection function.

Sept. 9, 1975 United States Patent [1 1 Berkovitz et al.

[ CLOSURE SYSTEM Inventors: Harry Berkovitz, Glen Rock; PrimaryExamifi1er Ev0n Blunk Lawrence Tosato, Minbum1 both of AssistantExaminer-James L. Rowland NJ.

Attorney, Agent, or FirmD Rv Lackey [73] Assignee: Westinghouse ElectricCorporation,

Pittsburgh, Pa.

ABSTRACT [22] Filed: Dec. 18, 1973 A closure system for an entrancewayhaving a door [2] 1 App! 426l8o mounted to open and close theentranceway. A perforated sill, in combination with a source of radiantenergy provides a plurality of vertical beams of radiant [52] US. Cl.187/52; 49/25; 250/22] B66B 13/26; EOSF [5/20 [5 l] Int. energy spacedacross the entranceway. A detector de- [58] Field of Search 187/52, 56,51, 48, DIG. l; vice is mounted to be responsive to at least one of the250/221; 49/25, 26, 27, 28 beams to detect interruption of radiantenergy to the detector device by an object in the entranceway. [n a [56]References Cited preferred embodiment, the source of radiant energyUNITED STATES PATENTS includes energy having a wavelength in the visiblespectrum, highlighting the sill as well as forming an 2/1934 Ellis187/52 9/1960 187/48 operative portion of the object detection functionvDrexler....,.........,...............,..

FOREIGN PATENTS OR APPLICATIONS 1 Claim, 4 Drawing Figures 685,7885/[964 Canada..,...,...........,....,,........ 187/52 PATENTED SEP 9 75SHEET 1 BF 2 NQI CLOSURE SYSTEM BACKGROUND OF THE INVENTION 1. Field ofthe Invention The invention relates in general to closure systems, andmore specifically to closure systems which include an object detectionfunction.

2. Description of the Prior Art In closure systems of the prior art,especially those used in elevator systems, it is common to provide somemeans for preventing the closure or door from striking an object in itsclosing path. One well-known type of door protective device employs abeam of radiant energy which is projected across the elevator caropening. Interruption of the beam by an object disposed substantially inthe closing path of the car and hoistway doors results in a modificationof the door operation, such as by stopping and reversing the doors.

Another commonly used type of door protective device is the mechanicalsafety edge. When the mechani cal safety edge, usually disposed on thecar door, is depressed, limit switches are actuated which are connectedin the door control circuits to effect a predetermined control action.U.S. Pat. No. 2,953,2l9, which is assigned to the same assignee as thepresent application, discloses a safety edge for the car door which isprovided by disposing transmitters of radiant energy and detectorsthereof on the car door, such that vertical beams of radiant energy aredisposed along the edge of the car door to detect objects having apredetermined relationship with the edge of the door.

As illustrated in U.S. Pat. No. 3,063,516, which is as signed to thesame assignee as the present application, it is also known, in a singleclosure system, to employ both the door edge protection, which iseffective when the door contacts or bears a certain predeterminedrelationship to an object, and protection for modifying the door actionwhen an object is detected in the door opening irrespective of thelocation of the door relative to the object.

SUMMARY OF THE INVENTION Briefly, the present invention relates to newand improved closure systems, and especially to new and improved closuresystems for elevators. An entranceway having a door mounted for movementto open and close the entranceway includes a sill, which in combinationwith a source of radiant energy, provides a plurality of substantiallyvertically extending beams of radiant energy spaced across theentranceway. The sill includes a plurality of spaced openings, with thesource of radiant energy being disposed below the sill. Thus, a singlesource of radiant energy may be used to provide a plurality of beams ofradiant energy, and this sin gle source is used, as set forth indifierent embodiments of the invention, to provide object detectionmeans without regard to the position of the object relative to the door,and/or object detection means for objects having a predeterminedrelationship to the edge of the door. In a preferred embodiment, thesource of radiant energy emits energy which is visible to the human eye,to provide the additional function of highlighting the sill of theentranceway.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may be better understoodand further advantages and uses thereof more readily apparent,

when considered in view of the following detailed description ofexemplary embodiments, taken with the accompanying drawings, in which:

FIG. 1 is a view in front elevation, with portions broken away, of anelevator car having a closure system embodying the teachings of theinvention;

FIG. 2 is a side elevation of the closure system shown in FIG. 1;

FIG. 3 is a fragmentary, cross-sectional, enlarged view of the closuresystem shown in FIG. 1; and

FIG. 4 is a schematic diagram of door control appara tus suitable foroperating the closure system shown in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS Although aspects of the inventionare applicable to closures designed for various applications, theinvention is particularly suitable for closures or doors employed inelevator systems. Consequently, the invention will be described withparticular relation to elevator closures or doors. Furthermore, aspectsof the invention are applicable to doors of various types, such ascenter-opening or side-opening, double or single, attendant-operated orautomatically-operated door assemblies. For the purpose of discussion,however, reference will be made to door assemblies of the horizontallyslidable centeropening type as employed in elevator systems.

Specifically, the closure system shown and described in US. Pat. No.2,992,818, which is assigned to the same assignee as the presentapplication, will be illustrated, and the control circuitry of thispatent is shown with the necessary modifications in the presentapplication to illustrate a control system suitable for operating aclosure in accordance with the teachings of the invention. Since adetailed description of the door control circuitry is available in U.S.Pat. No. 2,992,818, only the portion of the control circuit associatedwith the invention will be described in detail.

Referring to the drawings, FIG. 1 illustrates an elevator car having acenter-opening door 1 for opening and closing an elevator carentranceway 3 through which load may enter and leave the car. Thiselevator car may serve any desired number of floors or landings. Sincesuitable control mechanisms for elevator cars are understood in the art,further discussion thereof is unnecessary for an understanding of theinvention.

Car door 1 comprises two sections 5 and A5. In FIG. 1 the door is shownin its fully open position. A number of similar components are employedfor the door sections 5 and A5. Insofar as is practicable, a componentfor the door section A5 which is similar to a component for the doorsection 5 will be identified by the same reference numeral as isemployed for the corresponding component associated with the doorsection 5 prefixed by the letter A.

The door section 5 is provided with a door hanger 7 on which door hangerwheels 9 are mounted for rotation. The door hanger wheels for the doorsections 5 and A5 are positioned for movement along ahorizontally-mounted track II in a conventional manner. The track 11 issecured to the elevator car by any suitable means.

Movement of the door section 5 is effected by a lever I3 pivotallymounted on the elevator car by means of a pin 15. The lower end of thelever 13 is pivotally connected to one end of a link 17, the other endof the link being pivotally connected to the door section 5. Lever 13 iscoupled to the lever A13 by a link 19, the ends of which are pivotallyattached to the levers 13 and A13 by pivots 21 and A21, respectively.Pivot 21 is positioned above the pin 15, whereas the pivot A21 islocated below the pin A15. Consequently, rotation of the lever 13 toopen the door section moves the link 19 in the proper direction to openthe door section A5.

The lever 13 preferably is operated by a suitable door operator 23 whichmay include a reversible electric motor 25 coupled through suitablegearing to a shaft 27. The shaft 27 carries an arm 29 which is pivotallyconnected to one end of a link 31, the remaining end of the link 31being pivotally connected to the lever 13. Consequently, the motor 25may be energized in a conventional manner for the purpose of opening andclosing the door sections 5 and A5. When the door 1 is to be closed, themotor 25 is operated to rotate the arm 29 in a counterclockwisedirection as viewed in FIG. 1. in order to open the door, the electricmotor is reversed.

A control assembly 33 is mounted on the elevator car adjacent the motor25. Positive driven contact cams located in the control assembly 33control the rate of acceleration and deceleration of the door 1. Thecontrol assembly also houses control contacts and control resistors. Thecontact cams are keyed to the gearing associated with the motor 25 andoperate the control contacts for predetermined distances of travel ofthe arm 29 to vary motor armature circuit resistance, thus controllingthe doors rate of acceleration and of deceleration. Each cam issymmetrical and operates two spring-closed contacts, one contact beinglocated on each side of the cam. For each direction of door movement, aseparate and identical set of contacts is actuated, one for the openingmovement of the door, the other for the closing movement of the door.Such arrangement is well known in the art.

The elevator door sections 5 and A5 are each associated with a hoistwaydoor section, which sections are operable for opening and closing ahoistway entrance. FIG. 2 illustrates one of the hoistway door sections90. Although the hoistway door sections may be operated by anyconventional door operator, preferably the hoistway door sections areoperated by the door operator 23 on the elevator car through cooperativevane and drive block members (not shown). Thus, operation of the dooroperator mounted on the elevator car effects movement of both the carand hoistway door sections in unison.

During a closing operation of the car and hoistway door sections it isdesirable to provide object detection means which functions withoutregard to the position of the closing doors, and to also provide dooredge object detecting means which functions when the object bears apredetermined relationship to the door edge. FIG. 1 illustrates a newand improved closure system which provides either or both of thesefunctions with a single source of radiant energy. Further, the door edgedetector is provided without resorting to a mechanical edge, which mustbe retracted at the termination of each door closing operation, andwhich requires periodic maintenance due to its mechanical nature. Stillfurther, the single source of radiant energy is not mounted on the dooror doors of the elevator car, and it additionally may be used tohighlight the entry sill of the elevator car.

Specifically, the new and improved closure system employs a sill 92disposed at the entrance of the elevator car 1, which extendssubstantially across the width dimension of the entrance. The sill 92includes a plurality of openings 94 in the entrance portion of the sill,which openings may extend in spaced relation across the entranceway in asingle row. As illustrated most clearly in FIG. 3, the openings arepreferably formed by drilling counterbored holes, and protectivetransparent or translucent glass or plastic lens 96 are disposedtherein, such as with a suitable adhesive. The protective lens need notbe of the focusing type. The sill 92 is disposed to cover a recess orcompartment in the forward portion of the floor of the elevator car,immediately adjacent the entrance to the car 1. A source 98 of radiantenergy is disposed in this recess or compartment, just below theunderside of the sill 92 through which the openings 94 are disposed.This arrangement provides a plurality of vertically oriented beams 100of radiant energy spaced horizontally across the entranceway to theelevator car. The source 98 is preferably an electric lamp, such as anincandescent resistance lamp, or a mercury vapor lamp, such as afluorescent lamp. The wavelength of the electromagnetic radiation fromsource 98 may be selected from a wide range, and may be in the visibleor invisible spectrums. Radiant energy visible to the human eye has theadded advantage of highlighting the sill, and is thus the preferredembodiment, but infrared or ultraviolet wavelengths may be used ifdesired.

The first type of object detection which may be provided using thesource 98 and plurality of beams 100 of radiant energy is thearrangement, once activated during the door open cycle, which isindependent of the position of the door. For this arrangement, one ormore detecting devices responsive to the radiant energy used aredisposed in the ceiling or transom of the elevator car. For purposes ofexample, for a 42 inch centeropening door two detector devices 102 and104, spaced about 12 inches apart, will provide satisfactory objectdetection. However, any number of devices may be used. The detectiondevices should be rendered ineffective just prior to their detecting thedoor as the door closes, in order to prevent false triggering thereof.When two symmetrically located detectors 102 and 104 are used, asillustrated in FIG. 1, a single cam 106 and limit switch 108 may be usedto render devices 102 and 104 ineffective at av predetermined point inthe door close cycle.

The detector devices 102 and 104 may be of any type responsive to thewavelength of the radiant energy source. For example, they may be of thephotoemissive, photoconductive, or photovoltaic type, as desired. Thedetecting devices 102 and 104 may be connected to each control aseparate relay having a contact which is closed as long as the detectoris receiving radiant energy from source 98. Upon interruption of thisradiant energy to a detector, the contact of its associated relay wouldopen to effect some predetermined control action, such as stopping orreversing the doors, as will be hereinafter described relative to thecontrol circuitry shown in FIG. 4.

The single source 98 and perforated sill 92 may also be used to provideobject detection relative to the leading edge of a closing door panel,by mounting detector means on the door panel, or panels, adjacent theedge or edges thereof which lead upon closure of the door.

The detector means is spaced from the edge of its associated door panelto provide the desired detection zone, and as illustrated in FIGS. 1 and3 detector means 110 and 112 are provided for car door sections 5 and A5which preferably have at least two detector devices, such as detectordevices 1 14 and 1 16 which form a part of the detector means 1 l0.Detector device 1 14, which is closest to the leading edge of the doorpanel 5 upon closure therer-", is adjusted such that a hand placed uponthe door will interrupt a beam from the source 98 to the detector, andthus functions in a manner similar to the mechanical safety edge. If thedetector device 114 is spaced about one-half inch from the edge of thedoor, it will satisfactorily perform this function. The second detector116 is spaced from the door edge by a greater dimension. This dimensionis preferably selected to enable the detector 116 to detect an object inthe closing path of the door and to stop the car door before strikingthe object. A dimension of about 3 inches has been found to besatisfactory, but it is not critical. Since the detector means 110 moveswith the door, it is important that the number of openings 94, thediameter of the openings, the spacing of the openings and thus thehorizontal spacing of the resultant vertically oriented beams 100, andthe lens on the detector device, all be selected such that the detectorlens will span two adjacent beams 100 to maintain continuous contactwith the radiant energy, in the absence of an object interrupting theradiant energy, as the door moves from its open to its close position.One-half inch diameter openings disposed on three-fourths inch centershas been found to be satisfactory but other suitable dimensions may beused.

If desired, a detector 118 responsive to the radiant energy provided bysource 98 may be disposed in the recess with source 98. This detectormay include a relay having contacts connected to render detectors 102and 104 ineffective, and to energize auxiliary radiant energytransmitter devices 120 and 122, should the source 98 fail to provideradiant energy of a predetermined level. Transmitter devices 120 and 122are aimed at detectors means 110 and 112, respectively, to continue dooredge object detection until source 98 can be serviced.

Thus, the single source 98, in cooperation with the sill 92, provides aplurality of vertical beams 100 spaced across the entranceway to theelevator car 1, which beams are used to: (1) provide detection of anobject in the entranceway without regard to the position of the objectrelative to the doors, (2) provide detection of an object which contactsor bears a predetermined relationship to the leading edges of the doorsupon closure thereof, and (3) highlight the door sill when visibleradiant energy is used. The detection of objects is effective for boththe car and hatch doors, as it will be noted from FIG. 2 that the beams100 are located in the space between the car and hatch doors. The dooredge protection is achieved without mechanically actuable parts,increasing the useful width of the door opening, and reducingmaintenance.

In order to illustrate suitable operation of the door controller 33, aschematic control diagram is shown in FIG. 4 which will operate theclosure system shown in FIG. 1. In this diagram, the armature 25A andthe field winding 25F of the door operating motor 25 (FIG. 1) areillustrated. Electrical energy for the control circuits is derived froma pair of direct-current buses L+ and L-. The motor field winding 25F isconnected directly across the buses L+ and L-. In parallel with thefield winding 25F is a rectifier 35 of a conventional type, such assilicon. Current flows through the rectifier 35 in the directionindicated by its circuit symbol in FIG. 4. Thus the rectifier 35provides a path for induced current as a result of the collapse of themotor field windings magnetic field in the event that power is removedfrom the buses L+ and L-.

The motor 25 is energized to open or to close the car door by operationof a switch SW. Although this may be a manually operated switch, in apreferred embodiment of the invention this switch represents thecontacts of a relay or relays employed in any conventional dooroperating system to initiate an opening or a closing operation of thedoor. Thus, movement of the operating member of the switch SW up, asviewed in FIG. 4 to close its contacts SW1 completes, with a limitswitch 37 and break contacts CL] of a door closing relay CL, circuitconnecting a door opening relay OP across the buses L+ and L- forenergization. The limit switch 37 is opened as the door arrives at itsfully open position by a cam located in the control assembly 33.

Movement of the operating member of the switch SW down results inclosure of its contacts SW2 to complete, with a limit switch 39 andbreak contacts 0P1 of the door opening relay OP, a circuit connectingthe door closing relay CL across the buses L+ and L- for energization.The limit switch 39 is opened as the door arrives at its fully closedposition by a cam located in the control assembly 33.

The break contacts CLl prevent energization therethrough of the dooropening relay 0? when the door closing relay CL is energized. The breakcontacts 0P1 operate in a similar manner in the circuit of the doorclosing relay CL. Associated with the relay OP are make contacts 0P2 and0P4 and break contacts 0P3. Associated with the relay CL are makecontacts CL2 and CIA and break contacts CL3. These contacts controlenergization of the motor armature 25A, the circuits for energization ofthe armature being located in the lower portion of FIG. 2.

Associated with the armature 25A are a plurality of adjustable resistorsand a plurality of cam-operated control contacts for controllingacceleration and deceleration of the motor 25. These resistors andcontacts, together with the contact cams for the latter, are located inthe control assembly 33.

It will be noted that the adjustable resistor 41 is disposed in seriescircuit relationship with the armature 25A in the bus L+. The remainderof the adjustable resistors associated with the armature 25A bearidentifying symbols which are indicative of their functions. Thus, theadjustable resistor RAC is employed to effect acceleration of the motorduring a door closing operation while the adjustable resistor RAO isemployed for accelerating the motor during door opening movement.Similarly, the resistor RDCl is used for decelerating the motor andthereby the door during a door closing movement while the adjustableresistor RDO1 effects deceleration of the motor during door openingmovement. Likewise, the cam operated control contacts bear identifyingsymbols which are indicative of their control functions. For example,the contacts AC and A0 are effective for accelerating the door duringdoor closing and door opening movements, respectively. The contacts DCIthrough DC4 efi'ect deceleration of the door during door closingmovement and operate sequentially in the order of their suffix numerals.The contacts D01 through D04 in sequence similarly control doordeceleration during a door opening operation.

Make contacts ASC and A80 are disposed in series circuit relationshipwith the cam operated contacts DC4 and D04, respectively. These contactsare associated with an anti-stall or checkback relay AS. if a pair oflimit switches 43 and 45 both are in closed condition, the relay AS isconnected for energization across the buses L+ and L. In parallel withthe coil of the relay AS is resistor-capacitor network comprisingserially connected resistors 47 and 49 and a capacitor 51. In parallelwith the resistor 47 is a rectifier 53 of a conventional type such assilicon. Current flows through the rectifier 53 in the directionindicated by its circuit symbol in FIG. 4. Thus, when both of the limitswitches 43 and 45 are in closed condition, the capacitor 51 chargesthrough the resistor 49 and the rectifier 53, which, in effect, thenshorts the resistor 47. When one of the limit switches 43 or 45 isopened, the capacitor 51 discharges through the resistors 47 and 49 andthe coil of the anti-stall relay AS. Since the length of times of changeand discharge of the capacitor are dependent upon the RC network timeconstant, the rectifier 53 effects a fast charge of the capacitor 51 anda relatively slow discharge thereof.

The limit switches 43 and 45 are located in the control assembly 33 andare operated by cams disposed therein. In a preferred embodiment of theinvention, the cam associated with the switch 43 operates to open theswitch simultaneously with the opening of the control contacts DC4 byits associated contact cam. The limit switch 45 is opened by its camsimultaneously with the opening of the control contacts D04 by itsassociated contact cam. Each of these limit switches remains in opencondition from the time of its opening to the time when the door reachesthe same position in a door movement opposite in direction to that inwhich the door was moving when the respective limit switch was opened byits associated cam.

A door safety relay DR is connected across buses L+ and L via contactsC102 and C104 of radiant energy detectors 102 and 104 disposed in thetransom of the elevator car 1, contacts C114 and C116 of detector means110 which is mounted for movement with the door panel 5, and contactsC112 and C1 12' of detector means 112 which is mounted for movement withdoor panel A5. These serially connected contacts are associated withrelays (not shown) responsive to detectors 102 and 104, and to detectormeans 110 and 112, and these contacts are closed as long as itsassociated detector device is receiving radiant energy from source 98.Limit switch 108 is disposed to shunt contacts C102 and C104 when it isin its closed position, to render these contacts ineffective just beforethe radiant energy received by detectors 102 and 104 would beinterrupted by the closing door panels.

The door safety relay DR includes make contacts DRl and break contactsDR2. These contacts are illustrated in the position they would assume inthe event buses L+ and L- are not energized, or rclay DR is deenergizeddue to one of the contacts in series with the energizing coil of relayDR being open.

Contacts DRl are connected in series with the door close relay CL, andcontacts DR2 are connected to shunt contacts SW1 of switch SW. Thus,when relay DR is energized contacts DR] will be closed to enable thedoor close relay CL to be energized, and contacts DR2 will be open andthus will have no circuit effect. Should radiant energy to one of thedetectors be interrupted, relay DR will drop out, contacts DRl will opento deenergize the door close relay CL, and contacts DRZ will close toenergize the door open relay OP. Should it not be desirable to reversethe doors, contacts DR2 would not be required.

Relay M is a monitor relay responsive to contact C118 of detector 118shown in FIG. 1, which detector will maintain contact C118 closed andrelay m energized as long as the source 98 provides radiant energy.Relay M includes break contacts M1 and M2. Contacts M] are connectedacross contacts C102 and C104, and contacts M2 are serially connectedacross buses L+ and L with transmitter devices and 122, which are alsoshown in FIG. 1. Should source 98 fail to provide radiant energy of theproper level, contacts M1 will close to render the detectors 102 and 104ineffective, and contacts M2 will close to energize radiant energytransmitters 120 and 122, in order to retain the door edge objectdetection function.

In summary, there has been disclosed a new and improved closure system,especially suitable for elevator systems, which enables a single sourceof radiant energy to be used to provide an object detection function,which is independent of the position of the car doors, when the cardoors are open or in the process of closing, and an object detectionfunction which bears a predetermined relationship to the leading edge ofclosing doors. Further, this single source of radiant energy, ifselected to have a wavelength which is visible to the human eye, willhighlight the sill of the entranceway to the elevator car, adding to theappearance and visibility of the entranceway. While a singleincandescent tubular type lamp may be used, which would have arelatively low power consumption and thus long life, it is alsopractical to use a vapor tube, such as fluorescent tube, which has avery long life and low power consumption. A safety edge function isachieved without mechanical parts and need for retracting mechanism,which reduces maintenance cost, and since a mechanical safety edge isnot required, it adds usable space to the entranceway. The objectdetection function which functions without regard to the position of thecar doors, includes a transmitter and detector devices which arepermanently mounted on stationary portions of the elevator car. Even theobject detection function which bears a predetermined relationship tothe closing edge of a car door, only mounts detector devices on the cardoor, with the transmitter device being mounted on a stationary portionof the car.

While only two detector devices have been illustrated in the transom ofthe elevator car, a particularly wide opening to an elevator car couldbe divided into zones by using the required number of detectors in thetransom. The detectors, in addition to detecting objects for doormodification purposes, could also be used to count passengers, andindividual detection zones may be used to effect different dooroperations. For example, a central zone of a wide opening, upondetecting an object, may stop the car doors, while zones closer to thedoor edge may stop the car door and reverse its direction. While notshown in the drawings, a timer may be used to time the length of timethat the doors are held open in response to the object detection means.At

the end of a predetermined period of time, the door of said beams ofradiant energy, said detector protective devices may be overriden andthe doors means includingafirst detector device mounted to closed at aslow Speed. move with the door and provide an object detec- We claim asour invention:

tion zone adjacent the leading edge thereof upon 1. eievam' y qcomprising: closure, and a second detector device mounted on an elevatorf" havmg an entranceway, a stationary portion of the entranceway toprovide a door for emfanceway a stationary object detection zone in theentrancemeans mountm g said door for movement to open and way cioseSalci entralicewail' said detector means being responsive to an objectina sill associated with said entranceway, said sill ini terrupting theradiant energy received by either the eluding a portion which extendsoutwardly past the external side of said door when said door closesfirst or second detector device, for controlling the said entranceway,with this portion of said sill in- P? of f door d eluding a plural), ofspaced openings which auxiliary transmitter means mounted on the car oortend substantially across the entranceway, and at i dance a source ofradiant energy disposed below said Si and means responsive to thefailure of the source of providing a plurality of beams of radiantenergy f energy, for l 'g 531d auxl llary transwhich extendsubstantially vertically upward mmel means. (0 Provide a beam 0f ra ntnergy through the plurality of spaced openings in said sill, for thefirst detector device.

detector means positioned to receive at least certain

1. An elevator system, comprising: an elevator car having anentranceway, a door for said entranceway, means mounting said door formovement to open and close said entranceway, a sill associated with saidentranceway, said sill including a portion which extends outwardly pastthe external side of said door when said door closes said entranceway,with this portion of said sill including a plurality of spaced openingswhich extend substantially across the entranceway, a source of radiantenergy disposed below said sill providing a plurality of beams ofradiant energy which extend substantially vertically upward through theplurality of spaced openings in said sill, detector means positioned toreceive at least certain of said beams of radiant energy, said detectormeans including a first detector device mounted to move with the doorand provide an object detection zone adjacent the leading edge thereofupon closure, and a second detector device mounted on a stationaryportion of the entranceway to provide a stationary object detection zonein the entranceway, said detector means being responsive to an objectinterrupting the radiant energy received by either the first or seconddetector device, for controlling the operation of said door, auxiliarytransmitter means mounted on the car door and aimed at the firstdetector device, and means responsive to the failure of the source ofradiant energy, for energizing said auxiliary transmitter means, toprovide a beam of radiant energy for the first detector device.